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What is a "normal" pressure for my cartridge filter

The filter that came with the house is a Hayward C3020. It has 4 OEM 81 sq ft filters (CX580XRE).

Since I got smart enough to look (a few months ago), the pressure gauge has been at ~12 psi. The pump had been running 10 hours/day at least since November. I had no idea when the filters were last cleaned but I expected that I would see the psi creep up over time. Also, I read a few posts that said their "clean" pressure was ~20 psi. This got me worried that maybe there was a hole in the filter that was causing low pressure reading.

I just got finished cleaning the filters, and they seem like they are in good shape. No obvious hole, bands fraying but still intact. Put everything back together, and pressure now reads 9 psi.

The filters were absolutely caked with a whitish paste that I can't belive wasn't causing the pressure to increase more than a few psi. In the last couple weeks I have added:

Re: What is a "normal" pressure for my cartridge filter

I'm gonna have to guess just a little and say....

1. Yes. 9psi is on the low side of normal. If the cartridge looks undamaged, you simply have a circulatory system with a little less resistance than most....that's a good thing. Most pools check in around 10-15psi.

2. It's possible I guess you may have poured the chemistry in the skimmer a little too quickly. Although, baking soda and borax are quite soluble so it may be something entirely different. I'd clean it out and not worry about it. Previous owner may have tried to put some DE in it.

Re: What is a "normal" pressure for my cartridge filter

Every pool is different. You can't go by the pressures that other people see. If you have never done so, you should clean the filter to see what the starting pressure is just so you have a baseline to go by. Some filters can go an entire season without cleaning, others need attention far more frequently. The only way you can really know what to expect is to get experience with your particular filter.

Re: What is a "normal" pressure for my cartridge filter

I am debating biting the bullet and getting a new set of filters. At ~$200 it is a little steep, but at least I would be coming from a known starting point. After that no one to blame but myself.

Is adding DE a good idea on top of a cartridge filter? Whatever it was certainly left behind a huge mess after cleaning.

Hijacking my own thread, I am now reasonably sure that the previous owner had some borates in. As I stated in a previous post, he must have had something that saved me from algae bloom in the three months where I ignored the pool with FC @ 0. Before I added Boric acid, the Lamotte test was looking like 15 ppm, but the strips are so hard to read. I added 25 lbs which assuming a 0 staring point should have brought me to 30 ppm, but the test looked like at least 50. I redid the test and got my girlfriend to read it without any preconceived notions about where it should be and she said 50. I am going to consider my Borate-i-zation complete!

Re: What is a "normal" pressure for my cartridge filter

DE is not usually a good idea for cartridge filters. Double check your filter manual to see if they recommend it. A few cartridge filters are designed to work with DE, but most are slightly damaged by any addition of DE.

Re: What is a "normal" pressure for my cartridge filter

What size/model pump do you have and what size plumbing?

Normally, the filter media does not add much pressure to a cartridge filter so even if you had a hole in one, it would not change the pressure much. Lower than normal pressure is usually due to either a suction side restriction or an impeller clog.

Re: What is a "normal" pressure for my cartridge filter

Checking the impeller is fairly simple, open up the pump strainer basket and remove the basket. The impeller is down below the strainer basket and you should be able to feel around to see if there is any kind of debris in there. It should be completely clean in there.

Other suction side restrictions are sometimes a little more difficult to detect/locate. Check the skimmer basket, under the skimmer basket, look for good flow rates through the skimmer, make sure you haven't closed any suction side valves that are normally open, etc.

It is possible to get a fitting (drain king) for your garden hose that will allow you to flush water through the suction side piping backwards, which is a good way both to detect blockages and to clear them, but it requires that you have the right attachment for the garden hose.